Wear-resistant, polycrystalline diamond compacts (“PDCs”) are employed in a variety of mechanical applications. For example, PDCs are used in drilling tools (e.g., cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing machinery, and in other mechanical apparatuses.
PDCs have found particular utility as superabrasive cutting elements in rotary drill bits, such as roller-cone drill bits and fixed-cutter drill bits. A PDC cutting element typically includes a superabrasive diamond layer commonly known as a diamond table. The diamond table is formed and bonded to a cemented carbide substrate using a high-pressure/high-temperature (“HPHT”) process. The PDC cutting element may be brazed directly into a preformed pocket, socket, or other receptacle formed in a bit body. The cemented carbide substrate may often be brazed or otherwise joined to an attachment member, such as a cylindrical backing. A rotary drill bit typically includes a number of PDC cutting elements affixed to the bit body. It is also known that a stud carrying the PDC may be used as a PDC cutting element when mounted to a bit body of a rotary drill bit by press-fitting, brazing, or otherwise securing the stud into a receptacle formed in the bit body.
Conventional PDCs are normally fabricated by placing a cemented tungsten carbide substrate into a container with a volume of diamond particles positioned on a surface of the cemented tungsten carbide substrate. A number of such containers may be loaded into an HPHT press. The substrate(s) and volume(s) of diamond particles are then processed under diamond-stable HPHT conditions. During the HPHT process, a metal-solvent catalyst cementing constituent of the cemented tungsten carbide substrate, such as cobalt from a cobalt-cemented tungsten carbide substrate, liquefies and infiltrates into interstitial regions between the diamond particles. The cobalt acts as a catalyst to promote intergrowth between the diamond particles, which results in formation of a polycrystalline diamond (“PCD”) table of bonded diamond grains having diamond-to-diamond bonding therebetween that is bonded to the cemented tungsten carbide substrate. Interstitial regions between the bonded diamond grains are occupied by the metal-solvent catalyst.
Once formed, the PCD table may be leached so as to remove at least a portion of the cobalt or other metal-solvent catalyst, as the continued presence of such metal-solvent catalyst within the working surfaces of the PCD table can greatly decrease performance characteristics of the PCD table. For example, the wear resistance and thermal stability of a PCD table may be adversely affected by the presence of cobalt.
In order to accurately predict the quality and performance of PDCs, manufacturers and users of PDCs continue to seek improved non-destructive testing methods for testing PDCs.